Self-adjusting mechanism



Nov. 16, 1937. E s, WH-CHGER 2,098,987

I SELF-ADJUSTING MECHANISM Filed Dec. 18, 1936 $2M, fa /@4246:

Patented Nov. 16, 1937 UNITED STATES PATENT OFFICE SELF-ADJUSTING MECHANISM Eugene s. WitchgerjSaginaw, Mich.

Application December 18, 1936, Serial No. 116,655

Claims.

-This invention relates to improvements in automatic tappet adjusters, and pertains more par-' ticularly tosuch adjusters operated by so-called mechanical means, distinguished from those that function by hydraulic means.

An-object of my invention is toprovide a device fortaking up lost motion resulting from wear in the valve mechanism of an internal combustion engine, orfrom expansion of the cylinder block or other causes incident to the use of tappets in'engines orother machines.

"The operating principle of my improvement involves the use of housing elements arranged end to end and adaptedfortranslatory movements with-a tappet and also for movements toward and away from each other, and a closely wound coiled springthat is radially expansible in its free state, but-locks and becomes like a solid metal hoop "when suddenly compressed by inwardly directed force applied -to its rim. This locking result is attained by the frictional engagement of the convolutions-oi the coil with each other when the .coil is loaded at opposite portions of its diameter by tappet impingements upon the said housing elements, as in the normal operation of an engine.

A structure constituting an embodiment of my invention is illustrated in the accompanying drawing forming a part of this specification, in which: Fig. l is a side view of a tappet, partly in section, with my improved adjuster, shownin longitudinal section, mounted therein; an associated cam and valve stem being indicated by dotted lines.

Fig. '2 is a view of the adjuster shown in Fig. 1, as seen fromabove, the tappet being omitted.

Fig. 3 is a detached side view of the adjuster shown in 'Fig. 1.

"Fig. 4 is asimilar'view ofthe adjuster as seen in the'direction of the arrow, Fig. 3.

, 'fFig. 5'is a top plan View of the parts shown in Fig. 4, the upper housing member being removed.

Fig. 6 is a diagrammatic View showing the compressive loading of the spring coil.

' My automatic adjuster is shown and described inthe present application as a compensating device for taking uplost motion between the valve and the cam shaft of an internal combustion engine. However, it may readily be applied to other mechanisms to compensate for lost motion between an operating and an operated memberior members, itbeing understood that the present application is merely illustrative of one of the uses to which the invention may be put.

'It is adapted to be employed in mechanisms other than engines to automatically take up lost motion. Therefore, the terms tappet arid "tappets and the like are employed in the present specification and claims to designate all mechanisms to which the device as described, and the equivalents thereof, are adapted to be applied.

A closely wound annular coil of resilient ribbon metal I, which normally tends to expand radially outward, is interposed between two opposed memb'ers 2, 3 which together constitute a housing for the coil.

The members 2,3 are preferably cylindric and are arranged co-axially end to end in spaced relation. Conjointly, the members 2,3 are mounted to travel with atappet '4 which operates in the usual manner between a rotatable cam and a reciprocatory valve stem.

In addition to their translation, the members 2, '3 are capable of limited movement toward and awayirom each other, lengthwise of the tappet.

Guiding means, such'as bolts 5, connect the members together so as to permit the translation movement, the bolts passing freely through holes-'6 in'one of the members, as 2, and threaded in the other member 3.

The bolt heads, or nuts, I provide an adjustable stop means adapted to halt, at predeterminedpoints, the movements of members 2, 3 away from'each other, thereby limiting the permissible expansion of the coil spring I in the direction of the length of the tappet.

The bolts 5 also prevent relative rotation of the members 2, 3.

The adjacent ends of the members 2, 3 are so formed as to provide lengthwise slot-like recesses 8, :9 whose'inner peripheral walls present opposed concave bearing faces H), H, respectively. Preferably, each such face presents a substantially semi-circular seat that fits the outer face of the exterior convolution I2 of the coil l. The function of the seat is to exert pressure which is distributed over diametrically opposite portions of the coil, the amount of such pressure being appropriate to insure mutual frictional locking of the convolutions whenthe members 2, 3 are subjected to the thrusts of tappets under conditions of use in engines, or like machines.

The exterior face of the outer convolution l2 of the coil has a slight amount of peripheral sliding engagement with the bearing faces 10, 11. Under compressive actions of the character described the individual convolutions of the coil are brought into face-to-face engagement with each other, and they thereupon lock frictionally together at each working thrust of the tappet.

The coil I has sufficient expansible strength to force the members 2, 3 apart upon removal from them of the stresses intermittently applied by the tappet.

Guiding elements or lugs l3 are provided on one of the members, as 3, at opposite sides of spring 5. They span the clearance space between the members 2, 3 for the purpose of constraining the spring against undue expansion laterally.

In applying the device the member 3 is inserted in the end of the bore of a tappet and rests on a seat or shoulder M.

The member 3 is secured in place by spot welding or any other suitable means.

When the rotating cam drives the tappet 4 upward against the valve stem, which is loaded by means of the usual valve spring, not shown, the members 2, 3 are quickly forced toward each other, compressing the top and bottom portions of the coil i, such compression being applied over considerable areas of its outer convolution as is apparent in Fig. 1 and indicated by arrows in Fig. 6.

Sudden loading of such areas of the coil causes the individual convolutions to slip slightly upon each other peripherally and so tighten the coil, which was already closely wound. The convolutions are thereby frictionally looked upon each other. Thereupon the coil functions, in effect, as if it were a solid or unitary hoop of metal.

. When the cam and tappet have reached the top of their travel, and while they are moving downward to close the valve, the valve spring load remains on the coil l. During that part of a cycle of operation the coil, or spring I, is in its rigid or locked and compressed state.

. When the valve encounters its seat at the lower extremity of its downward travel the pressure on the coil is released suddenly. If, on account of expansion of the engine block or wear of the valve actuating parts the tappet is then 'too short to give a constant working contact between the cam and the end of the valve stem, the adjuster will at once take up the clearance and produce a quiet smooth operation.

The spring compensates for an increase in the length of the operating parts due to expansion. As the valve stem lengthens due;'say, to heating, its lengthening will occur over a period during which there are many cycles of tappet operation- For each tappet thrust there is a corresponding contraction of the spring-not enough to lock it, but sufficient to accommodate the small increment of increase in length of the valve stem. Over the period of stem expansion during heating the aggregate of such spring contractions is sufficient to keep the valve seating properly.

When the engine is running at speed the above mentioned operations, compressing, locking and then expanding coil I may occur as often as one or two thousand times per minute.

It will be observed that sidewise expansion of the coil, due to its compression, is avoided by contacting the guides l3, which are shown diagrammatically in Fig. 6.

Aside from the housing members 2, 3 there is only one moving part, namely the coil I, and this performs the functions of compressing instantly upon the application of load, of looking after the members 2, 3 have moved toward each other a short distance, thus preventing further compression, and of free expansion after the load is removed. In these essential respects the device herein described distinguishes from all others with which I am familiar.

Having shown and described a preferred embodiment of my invention wherein the adjusting device is made separate from the tappet, it will be obvious that the parts 3 and 4 may be made in one piece, and that the parts I and 2 may be removably applied thereto as above described, without departing from my invention as set forth in the claims.

Having thus described my invention, what I claim and'desire to secure by Letters Patent is:

1. An automatic tappet adjuster comprising co-axial cylindric members arranged end to end in spaced relation and adapted to be mounted for translatory movement with a tappet, means connecting said members to permit limited movement thereof endwise toward and away from each other, means preventing relative rotation of said members, adjacent ends of said members having lengthwise slot-like recesses whose inner peripheral walls present opposed concave bearing faces, a closely coiled annular resilient spring member of ribbon metal received between the said opposed bearing faces and normally tending to expand radially outward, the exterior surface of the outer convolution of said spring being in sliding engagement with the said bearing faces, and stop means adjustably associated with said members to halt their movements away from each other.

2. An automatic tappetadjuster comprising in combination a closely wound annular spring of resilient ribbon metal, interposed between 'two members arranged to be mounted to travel with a tappet and being movable toward and away from each other, a curved seat on each member fitting the outer convolution of said spring and adapted to apply thereto, at diametrically opposite portions of the periphery of the spring compression stresses such as are produced in the ordinary operation of tappets, to effect, at each impact, a frictional locking engagement of the convolutions of the spring upon each other, the expansible strength of said spring being appropriate to move said members apart upon release of such stresses.

3. An automatic adjuster comprising a compactly coiled annular spring made of resilient ribbon metal, a pair of opposed members capable of movement toward and away from each other, each member having a seat arranged to engage diametrically opposite portions of the exterior convolution of the spring and to exert thereupon an amount of distributed pressure appropriate to insure frictional locking of said convolutions upon each other when said members are subjected to thrusts under the conditions of use, said seats when released from such thrusts permitting expansion of the spring, and elements on said members at opposite sides of the spring to constrain the latter against undue lateral expansion.

4. An automatic adjuster comprising a compactly coiled annular spring made of resilient ribbon metal, a pair of opposed members capable of movement toward and away from each other, each member having a seat arranged to engage the spring at diametrically opposite portions of the exterior convolution thereof and to exert pressure thereupon when said members are subjected to thrusts under the conditions of use, the amount of such pressure being appropriate to insure frictional locking of said convolutions upon each other, said seats permitting expansion of the spring when released from such thrusts.

5. An automatic take-up mechanism comprising a coiled resilient spring, a pair of opposed members capable of movement toward and away from each other, each member having a seat arranged to engage the spring at opposite portions of the diameter thereof and to exert pressure thereupon when said members are subjected to thrusts under the conditions of use, the amount of such pressure being appropriate to insure locking of the convolutions of said coiled spring, said seats permitting expansion of the spring when released from such thrusts.

EUGENE S. WITCHGER. 

